Eresh-water Eiitomostraca of South America. 25 



ramus of the aritennæ. Only now and then does it make a 

 short excursion through the water, swimming about at quite 

 an even rate, and always with the back downwards. The males, 

 however, are much more agile, being in almost constant mo- 

 tion, only occasionally attaching themselves for a short while. 

 Occurrence. — The aquaria in which this form de- 

 veloped, were prepared with mud partly from Sâo Paulo 

 partly from Itatiba, and partly from Argentina. The speci- 

 mens examined by Mr. Richard were collected by Dr. v. 

 Ihering at Rio Grande do Sul. 



8. Siinocephalus Iheringi, Richard. 



(PL IV, figs. 10-13). 



Siinocephalus Iheringi, Richard, Entomostracés de l'Amérique du 

 Sud. Mém. Soc. Zool. de France 1897, p. 279. 



Specific Characters. — Female. Carapace in adult 



specimens, seen laterally, oval in form, considerably widening 



behind, dorsal margin almost straight in its anterior part* 



but behind forming an abrupt curve, ventral margin bulging 



in front, and passing behind with a bold curvature into 



the posterior one, which is rather oblique; hind projection 



of carapace very prominent, acutely pointed, and located 



a little above the axis of the body, being composed of 2 



juxtaposed lappets. Head comparatively small, and defined 



above from the carapace by a very small depression, dorsal 



margin rather convex in its anterior part, front somewhat 



deflexed and narrowly rounded at the tip, without any trace 



of denticles, ventral margin straight and horizontal, rostral 



projection well marked and somewhat procurved; fornix more 



prominent than in the preceding species. Sculpture of shell 



as usual, hind part of dorsal margin denticulate, the denticles 



